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5 Interactions found for:

Topamax and Synthroid
Interactions Summary
  • 2 Major
  • 1 Moderate
  • 2 Minor
  • Topamax
  • Synthroid

Drug Interactions

No drug interactions were found for selected drugs: Topamax, Synthroid.

This does not necessarily mean no interactions exist. Always consult your healthcare provider.

Drug and Food Interactions

Moderate
Synthroid + Food

The following applies to the ingredients: Levothyroxine (found in Synthroid)

The timing of meals relative to your oral levothyroxine dose can affect the absorption of the medication. Therefore, levothyroxine should be taken on a consistent schedule with regard to time of day and relation to meals to avoid large fluctuations in blood levels, which may alter its effects. In addition, absorption of levothyroxine may be decreased and/or delayed by foods such as soybean flour, cotton seed meal, walnuts, dietary fiber, calcium, calcium fortified juices and grapefruit or grapefruit juice. These foods should be avoided within several hours of dosing if possible. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

The following applies to the ingredients: Levothyroxine (found in Synthroid)

Using multivitamin with minerals together with levothyroxine may decrease the effects of levothyroxine. You should separate the administration of levothyroxine and multivitamin with minerals by at least 4 hours. If your doctor does prescribe these medications together, you may need a dose adjustment or special test to safely use both medications. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

Drug and Pregnancy Interactions

The following applies to the ingredients: Topiramate (found in Topamax)

Professional Content

This drug should be used during pregnancy only if the benefit outweighs the risk to the fetus.
-According to some authorities: Use is contraindicated unless there are no alternatives for epilepsy.

AU TGA pregnancy category: D
US FDA pregnancy category: Not assigned

Risk Summary: This drug can cause fetal harm when administered to a pregnant woman. Data from pregnancy registries indicate that infants exposed in utero have increased risk of major congenital malformations.

Comments:
-Inform women of childbearing potential of the potential risk to a fetus from exposure to this drug. Alternative treatment options may be advisable. According to some authorities, use is contraindicated in women of childbearing potential (the manufacturer product information should be consulted).
-Advise women of childbearing potential to use effective contraception during treatment. Estrogen-containing birth control may be less effective when used with this drug. According to some authorities, pregnancy testing should be performed prior to starting treatment, and contraception should be used throughout treatment and for at least 4 weeks after stopping this drug.
-A pregnancy exposure registry is available.
-Monitor pregnant patients and newborns of mothers exposed to this drug for metabolic acidosis and treat as appropriate. The effect of metabolic acidosis induced by this drug has not been studied in pregnancy; however, metabolic acidosis due to other causes in pregnancy can elicit decreased fetal oxygenation and growth as well as fetal death.
-According to some authorities, antiepileptic therapy should be continued during pregnancy using monotherapy at the lowest effective dose whenever possible. Folic acid supplementation (5 mg) should be commenced four weeks prior to and continued for twelve weeks after conception. Women should be followed by a specialist and offered detailed mid-trimester ultrasound.

Animal studies have revealed evidence of embryotoxicity and teratogenicity. There are no controlled data in human pregnancy; however, data from pregnancy registries have shown that infants exposed in utero have increased risk of cleft lip and/or cleft palate (oral clefts) and of being small for gestational age (SGA). SGA has been observed at all doses and appears to be dose-dependent.

To monitor the outcomes of pregnant women exposed to this drug, The North American Antiepileptic Drug in Pregnancy Registry has been established. Physicians are encouraged to register patients and pregnant women are encouraged to register themselves by visiting https://www.aedpregnancyregistry.org/join-our-study/.

Based on limited data, this drug has been associated with pre-term labor and premature delivery. In addition, metabolic acidosis induced by this drug may affect the ability of the fetus to tolerate labor.

AU TGA pregnancy category D: Drugs which have caused, are suspected to have caused or may be expected to cause, an increased incidence of human fetal malformations or irreversible damage. These drugs may also have adverse pharmacological effects. Accompanying texts should be consulted for further details.

US FDA pregnancy category Not Assigned: The US FDA has amended the pregnancy labeling rule for prescription drug products to require labeling that includes a summary of risk, a discussion of the data supporting that summary, and relevant information to help health care providers make prescribing decisions and counsel women about the use of drugs during pregnancy. Pregnancy categories A, B, C, D and X are being phased out.

References

  1. "Product Information. Topiramate (topiramate)." Advagen Pharma Limited (2025):
  2. "Product Information. toPAMAX (topiramate)." Janssen-Cilag Pty Ltd (2026):
  3. "Product Information. Topiramate (topiramate)." Viatris UK Healthcare Ltd (2025):

The following applies to the ingredients: Levothyroxine (found in Synthroid)

Professional Content

Use is considered acceptable.

AU TGA pregnancy category: A
US FDA pregnancy category: Not Assigned

Risk summary: No increased rates of major birth defects or miscarriages have been reported with use during pregnancy; untreated maternal hypothyroidism during pregnancy is associated with a higher rate of complications, including spontaneous abortion, gestational hypertension, pre-eclampsia, stillbirth, and premature delivery, as well as potential adverse effects on fetal neurocognitive development.

Comments:
-Thyroid replacement therapy should not be discontinued during pregnancy; hypothyroidism diagnosed during pregnancy should be promptly treated.
-Monitor TSH levels and adjust doses as needed.
-According to some authorities, combination therapy with antithyroid agents for hyperthyroidism is not recommended during pregnancy due to the risk of fetal hypothyroidism from higher doses of antithyroid agents crossing the placenta.

Animal studies have not been conducted. There is a long history of using this drug in pregnant women and this experience has not shown increased rates of fetal malformations, miscarriages or other adverse maternal or fetal outcomes. Hypothyroidism during pregnancy is associated with a higher rate of complications, including spontaneous abortion, pre-eclampsia, stillbirth and premature delivery. Maternal hypothyroidism may have an adverse effect on fetal neurocognitive development. Pregnant women taking this drug should have their TSH measured during each trimester and dose adjusted as appropriate. Patients will generally return to their pre-pregnancy dose after delivery. There are no controlled data in human pregnancy.

AU TGA pregnancy category A: Drugs which have been taken by a large number of pregnant women and women of childbearing age without any proven increase in the frequency of malformations or other direct or indirect harmful effects on the fetus having been observed.

US FDA pregnancy category Not Assigned: The US FDA has amended the pregnancy labeling rule for prescription drug products to require labeling that includes a summary of risk, a discussion of the data supporting that summary, and relevant information to help health care providers make prescribing decisions and counsel women about the use of drugs during pregnancy. Pregnancy categories A, B, C, D, and X are being phased out.

References

  1. "Product Information. Synthroid (levothyroxine)." Abbott Pharmaceutical PROD (2002):
  2. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
  3. Pharmaceutical Society of Australia "APPGuide online. Australian prescription products guide online. http://www.appco.com.au/appguide/default.asp" (2006):
  4. Cerner Multum, Inc. "Australian Product Information." O 0
  5. "Product Information. Levothyroxine Sodium (levothyroxine)." Fresenius Kabi USA, LLC (2021):
  6. "Product Information. Synthroid (levothyroxine)." AbbVie US LLC (2024):
  7. "Product Information. Tirosint (levothyroxine)." IBSA Pharma Inc. (2022):
  8. "Product Information. Thyquidity (levothyroxine)." Azurity Pharmaceuticals (2020):
  9. "Product Information. Levothyroxine Sodium (levothyroxine)." Glenmark Pharmaceuticals Europe Ltd (2025):
  10. "Product Information. Levothyroxine Sodium (levothyroxine)." SERB (2025):

Drug and Breastfeeding Interactions

The following applies to the ingredients: Topiramate (found in Topamax)

Professional Content

Benefit should outweigh risk

Excreted into human milk: Yes

Comments:
-The developmental and health benefits of breastfeeding should be considered along with the mother's clinical need for this drug and any potential adverse effects on the breastfed infant from this drug or from the underlying maternal condition.
-If this drug is used during breastfeeding, monitor breastfed infant for diarrhea, drowsiness, adequate weight gain, and developmental milestones, especially younger, exclusively breastfed infants.
-Some authorities recommend avoiding breastfeeding during therapy with this drug.

Limited data in women with epilepsy have shown drug levels in milk similar to those in maternal plasma. The excretion of topiramate has not been evaluated in controlled studies.

References

  1. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
  2. Cerner Multum, Inc. "Australian Product Information." O 0
  3. United States National Library of Medicine "Toxnet. Toxicology Data Network. http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen?LACT" (2013):
  4. "Product Information. Qudexy XR Sprinkle (topiramate)." Upsher-Smith Laboratories Inc (2017):
  5. "Product Information. Trokendi XR (topiramate)." Supernus Pharmaceuticals Inc (2017):
  6. "Product Information. Topiramate (topiramate)." Cipla USA Inc. (2017):

The following applies to the ingredients: Levothyroxine (found in Synthroid)

Professional Content

Use is considered acceptable

Excreted into human milk: Yes

Comments:
-Levothyroxine (T4) is a normal component of human milk; limited data on exogenous replacement doses during breastfeeding have not shown an adverse effect in nursing infants.
-Levothyroxine dose requirements may be increased in the postpartum period compared to prepregnancy requirements in patients with Hashimoto's thyroiditis.
-The presence of thyroid hormone in breast milk does not appear to interfere with neonatal thyroid screening.

References

  1. "Product Information. Synthroid (levothyroxine)." Abbott Pharmaceutical PROD (2002):
  2. Jansson L, Ivarsson S, Larsson I, Ekman R "Tri-iodothyronine and thyroxine in human milk." Acta Paediatr Scand 72 (1983): 703-5
  3. Moller B, Bjorkhem I, Falk O, Lantto O, Lafsson A "Identification of thyroxine in human breast milk by gas chromatography-mass spectrometry." J Clin Endocrinol Metab 56 (1983): 30-4
  4. Mizuta H, Amino N, Ichihara K, et al. "Thyroid hormones in human milk and their influence on thyroid function of breast-fed babies." Pediatr Res 17 (1983): 468-71
  5. Hahn HB, Spiekerman AM, Otto R, Hossalla DE "Thyroid function tests in neonates fed human milk." Am J Dis Child 137 (1983): 220-2
  6. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
  7. Pharmaceutical Society of Australia "APPGuide online. Australian prescription products guide online. http://www.appco.com.au/appguide/default.asp" (2006):
  8. Cerner Multum, Inc. "Australian Product Information." O 0
  9. United States National Library of Medicine "Toxnet. Toxicology Data Network. http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen?LACT" (2013):

Therapeutic Duplication Warnings

No warnings were found for your selected drugs.

Therapeutic duplication warnings are only returned when drugs within the same group exceed the recommended therapeutic duplication maximum.

Switch to: Professional Interactions

Drug Interaction Classification

These classifications are only a guideline. The relevance of a particular drug interaction to a specific individual is difficult to determine. Always consult your healthcare provider before starting or stopping any medication.

Major Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit.
Moderate Moderately clinically significant. Usually avoid combinations; use it only under special circumstances.
Minor Minimally clinically significant. Minimize risk; assess risk and consider an alternative drug, take steps to circumvent the interaction risk and/or institute a monitoring plan.
Unknown No interaction information available.

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